Detecting autism spectrum disorder in children with intellectual disability: which dsm-iv-tr criteria are most useful?

by Hartley, S.L. & Sikora, D.M.

Objective: The purpose of this study was to determine the efficacy of semi-structured parent interviews based on theDiagnostic Manual of Mental Disorders (4th Ed., text rev.) diagnostic criteria as a robust tool to differentiate children with autism spectrum disorders (ASDs) from those without autism spectrum disorders. Specifically, the study focused on older children with diagnoses of intellectual disability (IDs) as the high comorbidity and overlap of symptomatology make differential diagnosis difficult.

Method: Participants in the study included 89 children (aged 6-18 years) from an autism spectrum disorder clinic located in a large hospital in the northwestern region of the United States. All of the children in the study underwent a battery of cognitive, language, adaptive behavior and ASD measures, including a semistructured parent interview based on the DSM-IV-TR criteria. Eleven participants were given the Weschler Preschool and Primary Scale of Intelligence, Third Edition, and 48 children were given the Weschler Intelligence Scale of Children, Fourth Edition. Twenty-nine children were given the Stanford-Binet Intelligence Scale, Fifth Edition. Parents completed two standardized measures of adaptive behavior. Forty-two parents completed the Vineland Adaptive Behavior Scales, Second Edition, Parent/Caregiver Rating Form. Forty-seven parents completed the Adaptive Behavior Assessment System, Second Edition. All children were given the Oral and Written Language Scale. In addition, all participants were assessed using the Autism Diagnostic Observation Scale-Generic. Parent interviews were conducted using the Autism Diagnostic Interview-Revised. An interdisciplinary team (a licensed speech and language pathologist, developmental pediatrician, psychologist, and occupational therapist) conducted all of the assessments.

Results: To control for potential differences in subject characteristics between the older children with IDs and ASDs versus those with IDs but no ASDs a multivariate ANOVA (MANOVA) was conducted. One way ANOVAs were used to identify specific criteria that differentiated ASD from no-ASD groups. Within the Social Relatedness domain, there were significant differences between the ASD and no-ASD groups. Within the Communication domain, there was significant difference in two of the four indicators between the ASD and no-ASD group and finally, within the Restricted/Repetitive Movement/Stereotyped Patterns domain, only one indicator demonstrated a significant difference.

Conclusion: The DSM-IV-TR diagnostic criteria for autism spectrum disorders overlap in symptomatology and often co-occur with intellectual disabilities. It was found that older children with IDs and ASDs were best differentiated from those with IDs but without ASDs by using the diagnostic criteria in the Social Relatedness category. Older children with IDs and ASDs were more often reported to have difficulty initiating and sustaining peer relationships, poor nonverbal communication skills, deficits in seeking to share interests and poor social/emotional reciprocity. Fewer of the diagnostic criteria in the Communication domain were useful but stereotyped, repetitive behavior (hand-waving) and lack of imaginative play had a moderate effect size. It was further found that the diagnostic criteria in the Restricted/Repetitive/Stereotyped patterns domain was largely ineffective as both populations exhibit these behaviors.

Limitations of the study: All of the data collected for this study was done through a parent-interview and direct observation may help strengthen conclusions. All of the children in the study were referred to an ASD clinic and thus were more likely than the overall ID population to exhibit ASD characteristics. The study was conducted in a clinical setting which limits the generalizability of the conclusions. Interestingly, the authors note that the study was conducted with an “all or none” algorithm (i.e., the child either does or does not display the behavior). They noted that it may be more efficacious and meaningful to investigate degrees of severity. Both populations may exhibit deficits in seeking to share interests but the degree of severity may differ.